This is a question that many will face during this start-up season of the HVAC equipment that cools your homes, your office and perhaps even the data center that supports your mission. HVAC equipment, on average is engineered, depending on the specific manufacturer and the system type, to run for 15 - 20 years. Yes, many factors add or subtract to the life span ... maintenance, hours of operation during the course of a summer, operating environment, etc. As an example a church HVAC that operates on Wednesday evening & then heavy use on Sunday would certainly outlast an application of a 24x7 hour call center.
Then it happens, the technician responds to your crisis and you find out from him that you have a faulty XYZ ... What to do? The EPA is mandating that the current refrigerant that is most likely utilized in your system, Refrigerant 22, a common brand is Freon, made by DuPont, some are saying "No, replace the entire system", others will say, "We can just replace the R-22 and repair the faulty component" and yet another person will tell you to "Replace the refrigerant with Refrigerant 434a". Wow, that is a lot of info to process and by the way, you are hot or the technician wouldn't be there.
As in many situations, making a snap decision is not ideal. Having some time to ponder, review proposals, etc. is always a nice luxury. Problem is, emergencies are just that, they pop up with no warning. AirTight FaciliTech, as any reputable resource should be, will work with you in advance to plan for the day of reckoning. How old is your system, do you own it or just maintain it (Think Triple Net Lease) how long will you inhabit the building, plant, facility or house ... Many, many variables.
This decision always comes back to logic. Analyze the options, decide on your timing, plan and budget for the expense, work with a quality, licensed and insured contractor and develop that all important roadmap. When you are kicked back in comfort, your internal voice can the tell you, "Nice Job!"